Multiple-path water-cooled furnace



{Sheets-Sheet E F NORTHRUP MULTIPLE PATH WATER COOLED FURNACE Flled July 13, 1923 im-JEN :5.

Aug. 28, 1928.

E. F. NORTHRUP MULTIPLE PATH WATER COOLED FURNACE Aug. 28, 1928.

Filed July '13, 1923 2 Sheets-Sheet 2 Patented Aug. 28, 1928.

' UNITED STATES PATENT OFFICE.

EDWIN F. NORTHRUP, OF PRINCETON, NEWJERSEY, 'ASSIGNOB '10 AJAX ELECTRO- THERMIC OORIPOBATION, OF TBENTON,'NEW JERSEY, A. CORPORATION OF NEW JERSEY.

Application filed m 13,

A further purpose is to form the inductorof an induction furnace of a hollow edge-.

wound conductor having. relatively great width extending radially and flattened to se-.

cure a maximum number of turns per inch, and to water cool the inductor coil to permit maximum current carrying capacity within each turn so as to obtain a field having,high

concentration of ampere turns.

A further purpose is to compensate for the high water resistance of the narrow passage provided, by the use of multiple paths of flow for the water, preferably with the electric current flow in series through all the paths but permissibly having these electric paths also in multiple.

A. further purpose is, by the combination of edge-wound coil and multiple-path water cooling .to overcome previously existing difliculties with low frequency induction furnaces having no inter-threading of transformer iron, concentrating the effective am- 3 pere turns upon the charge through increase both of the number of turns per inch. and of the effective carrying capacity of each turn.

A further purpose is ,to apply low frequency; inductive heating without necessity for transformer iron interlinkage to the melting out of low-melting point cores from within' automobile tires.

Further purposes will appear in the specification and in the claims.

40 I prefer to illustrate my invention by a few applications only, selecting forms which have proved to be practical, eflicient and highly advantageous and which at the same time well illustrates the principles of my in- 4 veution.

Figure 1 is a central section of a furnace to which my invention is applied.

Figures 2, 3, 4 and 10 are corresponding "iews of slightly diflerent forms.

Figure MS a longitudinal section of an inducto'r embodying my' invention applie within the interior of atube.

Figure 6 is a side elevation showing one lhIULTIPLE-PATH WATEE-GOOLED FURNACE.

1923. Serial No. 851,398.

inductors for induction furnaces having a single inlet and single outlet for the water and having a slightly oval or elongated cross section of the individual water-cooling inductors.

It has been generally understood in the past that induction furnaces could not be operat'edon commercial-frequencies for use upon a material which is not itself ma netizable without inter-threading of trans ormer iron. The reason of this has been that it has been considered impossible to get'sufiicient in- .mercial frequency practicable for the .pri-

maries of induction furnaces without interlinkage of iron. Two factors have made this possible; the one is the flattening of the section of a hollow inductor so much as to greatly increase the number of turns per unit of ossible to so length of the furnace coil; and the other is the provision of multiple flow of water through, the hollow inductor used so as to permit crowding of the primary conductors to the limit of current which they can carry properly while cold.

The first factor affects the number of turns andthe second the number of amperes and each cooperates with the other as a multiplier I to secure a. maximum of ampere turns with a corresponding maximum of input per unit of length of the coil.

1 In Figure 1 I have shown a furnace of the stationary. cylindrical type havinga base 10, an outer protective cylinder 11' whlch is preferably not only mechanically protective but space between the crucible and the insulating cylinder 12. This powdered refractory may be Withdrawn, permitting withdrawal of the crucible by the removal of a slide 15 upon which the refractory rests and which slide is movable in guides 16.

A top 17 and lid 18 of heat insulating material close the upper part of the furnace.

The induction coil 19 is spiral. It is shown as, and preferably is, connected in series elec trically from end to end, the current being applied through terminals 20 and 21. v

The coil is shown as comprising a helix of copper tubing of very fiat section as at 22, through whichwater is passed in multiple from inlets 23, 24 and through inlet tubes 25 at the top and bottom and out by outlet connection 26.

Where the electrical connection is different from the water coii'nection (i. 0., one in series and the other in parallel as here, or with parallel electrical connections not corresponding to the points of water connection) insulating tubing is used for the terminals or is interspersed between the sections to provide insulation.

My invention does not reside in the dimensions selected and will operate with a variety of dimensions. For the purpose, however, of giving one concrete illustration that works satisfactorily I will state that I have used copper tubing for the inductor with good results, which tubing was flattened to approximately 1%" in the long dimension of its cross-section and to a width of cross-section but little greater than twice the thickness of the metal walls, giving a cross-section for water flow of nearly one and three-sixteenths by approximately one-thirtieth of an inch. This was a high duty 60 cycle'installation.

Since the resistance to water flow through a coil having flow resistance 1- from end to end varies inversely with the square of the number of sections the division of the coil into two paths in multiple reduces the resistance to one-fourth with increasing benefit where the number of sections is increased.

\ As will be seen, there are two paths only for the water here which have proved quite sufiicient for a small furnace.

- In Figures 2 and 3 the crucible 13 lies lower i. e., closer to the base 10', and there is no opening through the base. In each a plurality of inlets 25 is shown interspersed with outlets 26.

In Figure 2 the winding/i'sfcontinuous for the entire inductor coil, whereas in Figure 3 the inductor coil is split up into a plurality one with another.

of inductor coils or sections, as in Figure 9, which are both electrically and hydraulically in parallel and which together comprise the complete inductor coil.

In Figure 2 the cross section of the tubing I water respectively. Either low frequency or high frequency may be applied through the flattened section of Figure 2, for example,

and the multiple water flow cooperate each as a multiplier to increase the concentration of ampere terms to a maximum and hence find special utility in the lower frequencies.

In Figure 4 the electric current is applied in' series from conductors 27,28 and the water flows in multiple through a flattened hollow coil section which may havea single inlet and multiple outlets or a single outlet and multiple inlets as preferred. The inductor is here applied to a pan or kettle of relatively large diameter.

In Figure 5 the coil 19 is shown as inside a tube 29 and as having a plurality of inlets 25 and a single outlet 26 interior to the coil.

In Figures 6, 7 and 8 the coil receives current in series from conductors 27, 28 and has a single inlet or outlet with multiple outlets or inlets as the case may be for water cooling. In this case the coil surrounds a rubber tire 30 upon a rim 31 and is for the purpose'of melting out a metal core 32. The metal core is used in molding the tire, and must be removed prior to use. It is normally of lead or of an alloy having a low melting point.

The interior of the tire and the rim are apertured at 33 to provide for removal of the melted core material which will flowout as melted until the level of the top of the rim opening is reached from which point it mayv ably iron drum 35 for the purpose of heating the drum and through it controlling the contents of the drum. 7 In each coil or section the electrical current is in seriesbut the several coils or sections are electrically in parallel, Together they make up the complete inductor coil. This would apply equally well of course, tothe heating of electrically conducting contents of a tube,

pipe or drum which is itself of non-magnetic or non-conducting material or to heat a solid material at different parts of its length or extent.

In Figure 10 the general construction of llll) tor, distributed along the surface of a prefer- Figure 1 is shown with the distinctions that the furnace is shorter and that the pipe is here of circular cross section. One inlet and two outlets here take the place of the two inlets and one outlet of Figure 1.

It will be obvious that the word furnace as used herein does not require a melting furnace but will apply also to heating devices where melting does not take place.

It will be obvious that the construction and method included herein have all the advan tages of the constructions and methods of my previous patents in permitting the use of any standard form of crucible without alteration to provide for interlinliage of transformer iron, that the invention is independent of the size and shape of the article heated whether a conducting container or the material to which the heat is to be directly applied and that the external and internal application of the coil to pipes ortubes will apply equally well to solid material (where outside) drums or other casings or containers.

It will also be evident in view of my disclosures in my Patents Nos. 1,286,394 and 1,286,395 that any adjustment or correction of power factor may be made in the current supply which may be required.

It will be obvious that various changes may be made in the construction and application of my invention in view of the disclosure herein while taking advantage of all or a part of the benefit of my invention and it is my purpose therefore to'include herein all such changes as come within the reasonable spirit and scope of my claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is f 1. In an electric furnace, a hollow inductor. furnace coil of highly conducting tubular material, in combination with means for supporting the charge to be heated Within the coil and a source of water cooling therefor providing multiple paths from inlet to discharge through different sections of the coil.

2. In an electric furnace, a furnace coil of hollow flat tubing of highly conducting material, the depth of the opening radially being many times its width parallel with the axis, having the turns of the'coil close together to provide a maximum of current carrying capacity for a minimum of conductor width, in combinationfwith means for supporting the'charge to be heated within the coil and water cooling for the said coil.

3. In an electric furnace, a furnace coil of hollow flat tubing of highly conducting ma: terial, the depth of the opening radially be- '-ing many times its widthparallel with the axis, having the turns of the coil close together to provide a maximum of current car- 'rying capacity for a minimum of conductor 'width, in combination with I means for supporting the charge to be heated within the coil and water cooling for the said coil providing multiple paths of water flow through the coil from the point or points of inlet to'the point or points of outlet.

i. In an electric furnace, a furnace coil of hollow fiat tubing of highly conducting material having the-turns of the coil close together to provide a maximum of current carrying capacity for a minimum of conductor width, in combination with means 'for supporting the charge to be heated within the coil and water cooling for the said coil providing multiple paths of Water flow through the coil from the point or points of inlet to the point or points of outlet and a source of low frequency current'supply for the coil.

5. In a low frequency induction furnace, the combination of a single layer hollow, induction furnace coil flattenedto provide great radial depth and narrowaxial extension, water cooling for the coil through multi le paths therein, means for supporting the 0 large. to be heated within the coil and asource of low frequency electric current supply in series with the coil. i i

6. A furnace inductor coil comprising a flat tubular conductor .helieally wound, adapted to surround the charge and free from interlinkage with transformer iron, in combination with a source of current therefor, means for supporting the charge to be heated within the coil and a plurality of inlet and outlet'water cooling connections therefor.

7. A furnace inductor coil, comprising a single layer of coaxialturns each of flattened conductor, having the opening in the conductor of a depth radially of the coil many times the width axially of the coil, having a plurality of inlet and or outlet water connections for multiple flow of Water through different Yo I sections of its length, heat insulation within the coil and a crucible within the heat insulat1on. I

8. A furnace inductor COll, comprising a .single layer of coil turns each of edge Wound conductor flattened to make the opening of depth radially many times the thickness parallel with the axis and a magnetically and electrically conducting cylindrical body within the coil, insulated therefrom and adjacent the inner edges of the coil.

9. As a new article of manufacture, an inductor furnace coil of conducting tubing flata combination of a coil of edge-wound flattened tubing having the opening between the side walls of the tubinga proximately equal to the wall thickness of t e tubing, in combination with means for passing cooling fluid through the tubing.

12. In an electric furnace inductor, the combination oiia coil ofedge-wound flattened tubing having the opening between the side walls of thetubing approximately equal to the wall thickness of the tubing, insulation between the successive turns of the tubing and means for supplying cooling fluid to the tubing, the metal filling substantially half of the entire cross section of tubing, water and insulation. I

13. The method of heating byelectrical induction which consists in circulating low frequency current about the charge to be, heated, concentrating the ampere turns of the low frequency current applied by utilizing a flat tubular conductor edge-wound to increasethe number of turns by reducing the axial length occupied by each turn, winding the turns closer together than the initial diameter of the conductor and water cooling the coil to keep its resistance and temperature low.

14. The method of heating by electrical induction which consists in circulating low frequency current about the charge to be heated concentrating the ampere turns of the low frequency current applied by utilizing-a hollow inductor at a high current concentration wound at a closer spacing than the initial diameter of the inductor tubing and in keeping the temperature and resistance down by passing water through the turns in multiple.

15. The method of heating b electrical in duction which consists in circu ating low frequency burrent about the charge to be heated, concentrating the ampere turns of the low frequency current applied by utilizing a hol-v low inductor of flattened section having a large radial section depth as compared with the thickness wound at a closer spacing than the initial diameter of the inductor tubing and in keeping the temperature and electrical resistance low notwithstanding the high fluid resistance due to the flat section by passing water through the inductor in multiple.

16. The method of obtaining high concen- "tration of ampere turns in an electrical in-' duetor furnace which consists in utilizing a hollow inductor, in passing the electric current through the inductor in series while passin Water for cooling purposes through the in uctor in multiple and passing current through the inductor at a higher rate than would be ermissible with'the less effective cooling it, he water cooling were applied in series at the'same pressure. x 17 The method of obtaining high concentration of ampere turns in an electrically conducting casing of magnetic material within which consists in forming the coil as a the col duction at a frequency whic duct/ion at a frequency whie able for cooling.

1, es1,9so

width parallelto the length of the casing,

winding the turns very close together and passing current through the turns.

18. The method of heating b electrical inis not high which consists in concentrating the ampere turns of the current applied by providing a metallic current path of spiral form having for each turn a narrow width axially and a much greater depth radially than its width so as to yield a large cross section per turn of coil length and internally cooling the metal forming the path.

19. The method of heating by electrical induction at a frequency which is not high which consists in concentrating the ampere turns of the current applied by providing a metallic current path'of spiral form having for each turn a narrow width axially and a much greater depth radially than its Width so coil length, spacing the paths less along the axis, one from the next than the width of the path and water cooling the path in multiple tion to water cooling.

20. Themethod of heating b electrical inis not high which consists in concentrating the ampere turns of the current appliedby flattening a conducting tube toan interior width across the tubenot much in excess of the double thickness of tube wall, in winding the tube edgewise in the form of a coil of but slightly larger interior coil diameter than that of the intended charge and in which the'turns are through the interior, thus reducing the fricclose together to give a maximum of'numberof turns of hollow conductor and of cross sec tion of metal per unitof single turn coil length and in water cooling the tube through the hollow of the tube thus flattened.

21. In electric induction furnace construction and operation, the method of increasing the current-carrying capacity of hollow water-cooled conductor per unit of single layer coil length which consists in flattening the conductor, winding it edgewise about the space for the charge, with spacing from turn center to turn center less than the initial diameter of the conductior,to increase the number of turns per -.unit of coil length, thus maintaining the same surface of water contact on the interior for water cooling while reducing the water content and'increasing the friction to Water passage, and in passing Watefthrough various parts of the total induc tor in multiple to reduce the fluid resistance met and increase thequantity of wateravail- EDWIN F. NORTHRUP. 

